when (NimMajor, NimMinor) < (1, 4):
  {.push raises: [Defect].}
else:
  {.push raises: [].}

import std/sequtils, stew/[byteutils, endians2, arrayops], nimcrypto/sha2
import ../topics, ./message

## 14/WAKU2-MESSAGE: Deterministic message hashing
## https://rfc.vac.dev/spec/14/#deterministic-message-hashing

type WakuMessageHash* = array[32, byte]

const EmptyWakuMessageHash*: WakuMessageHash = [
  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  0, 0, 0,
]

converter fromBytes*(array: openArray[byte]): WakuMessageHash =
  var hash: WakuMessageHash
  discard copyFrom(hash, array)
  hash

converter toBytesArray*(digest: MDigest[256]): WakuMessageHash =
  digest.data

converter toBytes*(digest: MDigest[256]): seq[byte] =
  toSeq(digest.data)

proc computeMessageHash*(pubsubTopic: PubsubTopic, msg: WakuMessage): WakuMessageHash =
  var ctx: sha256
  ctx.init()
  defer:
    ctx.clear()

  ctx.update(pubsubTopic.toBytes())
  ctx.update(msg.payload)
  ctx.update(msg.contentTopic.toBytes())
  ctx.update(msg.meta)
  ctx.update(toBytesBE(uint64(msg.timestamp)))

  return ctx.finish() # Computes the hash